# @algorithm @lc id=857 lang=python3 weekname=weekly-contest-83
# @title positions-of-large-groups


from cn.Python3.mod.preImport import *
# @test("abbxxxxzzy")=[[3,6]]
# @test("abc")=[]
# @test("abcdddeeeeaabbbcd")=[[3,5],[6,9],[12,14]]
# @test("aba")=[]
class Solution:
    def largeGroupPositions(self, s: str) -> List[List[int]]: